Insulation is generally required to protect a rocket motor case from the hot corrosive gases resulting from the combustion of the solid rocket motor propellant contained within the rocket motor case.
In one conventional process for fabricating and installing the insulator in an interceptor/missile motor, if required, the steps described below are employed. The function of the insulator is to provide thermal protection to the motor case. The process is time consuming and costly because the insulator is prepared in three segments, namely, the forward dome insulator, the aft dome insulator, and the motor case side wall insulator. The forward and aft dome insulators are laid up in female molds using calendered sheets of insulator to obtain the required thickness. Several different thicknesses are required to provide the insulative requirements, and are predominantly influenced by the combustion flame temperature of the propellant and its internal grain configuration. The insulation segments are cured, then the forward and aft dome insulators are bonded into the motor case using an adhesive. The center section of the insulator is next laid up. A bladder is inserted into the motor case and inflated. The bladder pushes the insulation up tightly against the interior of the motor case. The center insulation is then cured, and the bladder is removed. The propellant casting mandrel is inserted, and the propellant cast into the insulated motor.
U.S. Pat. No. 4,596,619, which was issued to John D. Marks on Jun. 24, 1986, discloses apparatus and another method of making an elastomer lined composite vessel having a dome-like shape. This method employs a thin, tacky ribbon comprising elastomer which an applicator moving relative to the rotational axis of a rotating mandrel causes integral segments of ribbon to adjacently position and tack together on the surface of the mandrel thereby covering the mandrel, including the dome-like shaped portion. Filament winding a casing comprising filaments and thermosettable resin around the elastomer layer is next completed, and the thermosettable resin and elastomer layer is cured to yield a composite vessel.
Thus, composite vessels and composite rocket motor cases as presently constructed require resin preparation, fiber impregnation, or debulking and compaction of wound structures when filament is employed. In most structures requirements for external and internal motor case insulation exist. Thermosetting resins, such as epoxy resins, are employed in various processes. When the thermosetting resins are polymerized during curing, they cannot be softened, recovered, and recycled. Therefore, the presently used materials are not attractive for recycling as they must be scrapped. Because of environmental restrictions any materials which are presently scrapped have to be disposed of in an acceptable manner. Disposing of these materials in an acceptable manner whether it be by approved burning or disposing to landfills adds considerable cost to waste disposals since environmental laws place restrictions on disposal operations to guard against polluting the environment.
The desirability of providing a recyclable thermoplastic resin for use in the fabrication of high temperature-resistant rocket motor cases is recognized.
An object of this invention is to provide non-composite, thermoplastic, high temperature-resistant rocket motor cases.
A further object of this invention is the employment of a thermoplastic resin in the fabrication of interceptor rocket motor cases.
Still a further object of this invention is the employment of a thermoplastic resin which serves as both an insulator and an interceptor rocket motor case material.